In recent years, wireless communication devices conducting wireless communication based on Bluetooth (registered trademark), which is a short distance wireless communication standard, have increasingly been in use.
For example, Unexamined Japanese Patent Application Kokai Publication No. 2009-118403 discloses a time correction system comprising a cell-phone device and wrist watch type terminal device conducting short distance wireless communication. In this time correction system, the cell-phone device sends time information to the wrist watch type terminal device and the wrist watch type terminal device corrects the measured time based on the time information.
Triggered by a user operation or an internal event within the cell-phone device that occurs periodically, the time information is sent and received. Moreover, the time information is sent and received again if the response time of the wrist watch type terminal device to respond with notice of completion of time adjustment since the time information is sent by the cell-phone device exceeds a given time period.
When a cell-phone device and a wrist watch type terminal device conduct short distance wireless communication as in the Unexamined Japanese Patent Application Kokai Publication No. 2009-118403, the wrist watch type terminal device sends advertisement to the cell-phone device and the cell-phone device responds with a connection request, whereby the connection is established. Here, the advertisement is notification information for giving notice of presence of the self.
A prerequisite for realizing the transmission/reception of time information in the Unexamined Japanese Patent Application Kokai Publication No. 2009-118403 is that the connection is established as described above. Therefore, the wrist watch type terminal device has to be so programmed as to send advertisement at a timing corresponding to a user operation or an internal event that occurs periodically in the cell-phone device.
The Unexamined Japanese Patent Application Kokai Publication No. 2009-118403 describes embodiments in all of which the cell-phone device and wrist watch type terminal device deal with each other on a one-to-one basis. In other words, no embodiment is described in which the cell-phone device time-synchronizes multiple wrist watch type terminal devices.
Generally, specification for simultaneously connecting multiple wrist watch type terminals to the same cell-phone device is complex and the necessity of such a configuration is rare. Therefore, presumably, the cell-phone device in the Unexamined Japanese Patent Application Kokai Publication No. 2009-118403 is specified to establish connection to one wrist watch type terminal device at a time where there are multiple wrist watch type terminal devices to connect.
Moreover, normally, the initial value for timing transmission of advertisement for automatic time correction (the automatic time correction time) is set to the same time for all wrist watch type terminal devices. This is because even if the initial values for the timing are randomly set, the timings may overlap and some difficulty in mass production may arise.
Therefore, when the cell-phone device time-synchronizes multiple wrist watch type terminal devices in the time correction system of the Unexamined Japanese Patent Application Kokai Publication No. 2009-118403, the timings of connection for automatic time correction of multiple wrist watch type terminal devices are set to the same time (for example, 5:00 AM) in some cases. In such cases, the multiple wrist watch type terminal devices send advertisement to the cell-phone device all at once at the timing of connection. However, the cell-phone device cannot establish connection to multiple wrist watch type terminal devices at the same time; therefore, unsuccessful connection occurs. As unsuccessful connection occurs, the wrist watch type terminal device is not time-synchronized.